3.1 running very rich+backfiring...

[lincolnolli]

Hello!
I've bought a 92Firebird 3.1 from a friend.Lately we have a lot of trouble with the engine.It suddenly would run very rich with a lot of smoke coming out.Feels like a carb motor with too much choke.It wants too clear only at full throttle,but only for a second,then it dies.Pops+smokes like hell!
Sometimes the car drives nice for an hour or two...
There was a code for MAT,changed it but nothing...
Also tried a used but good ign module,from a V8 Caprice.
Since i found this very useful site,i checked the MAT+coolant sensors for resistance.Both were around 3.4kOhms,which i think is nice with the cold engine..
Now i tested the coil which all looks good,except the secondary resistance,which is 8kOhms.Is that OK???

Thank you very much!!
Olli,from Berlin/Germany

[geoffinbc]

Try these.

http://members.shaw.ca/betterthanyoutoo/coiltest/coiltest.htm

http://members.shaw.ca/betterthanyoutoo/pickupcoiltest/pickupcoiltest.htm

Also check the Engine coolant temperature sensor. It should read 3400 ohms at 21*C(70*F) so test at room temperature.

[lincolnolli]

Thanks

Thank you!
All sensors are OK.But today i found that the Computer sometimes gives the wrong voltage out.I had 0.9 to 9Volts coming out of the TPS!!
Then i checked the computer output voltage on several sensors.
It climbed sky high,sometimes up to 18Volts!Then it goes back to a steady 5V,then up again....
Cause i learned electronics,i opend the computer and found one transistor/IC that is big enough to be the "stabilizer".Maybe i should try a 7805 or similar ic to give the sensors a steady 5V again??
Can you tell me if this is a typical problem with these ECM's??

This is a real bad situation,since you can't get a new one round here.I only found a 1988 2.8 ECM,which only has 2 connectors.But i need the box with three...

Any help would be very nice.
Thanks!

Olli
Berlin/Germany